Joint Scheduling and Channel Allocation in Wireless Mesh Networks

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Joint Scheduling and Channel Allocation in

Wireless Mesh Networks

Nguyen H. Tran and Choong Seon Hong

Consumer Communications and Networking Conference (CCNC), 2008.

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Outline

Introduction System model Fair scheduling and Channel allocation

algorithm Performance evaluation Conclusion

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Introduction

Wireless Mesh Networks (WMSs) Routing Scheduling Channel allocation

Interference Multiple radios, simultaneously Limited number of channels available Signal noise interference rate (SNR)

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System model

Network model Network graph G(V, E)

V: the set of nodes (mesh routers) E: the set of links

Qe(t): number of packets waiting to be transmitted on link e by the end of time slot; as queue length of e

K orthogonal channels (each node has one or more than one wireless interface cards)

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Interference model - physical interference model

packets along link (i, j) are correctly received when

RSSij: signal strength of node j when node i

transmits to node j ISSi

j: interfered signal strength from another node k also transmitting

N: white noise Vs: the subset of nodes in V that are

transmitting concurrently

threshold

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Interference model - interference graph

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Conditions

G’T = {e1, …, ek} E: certain edge set of transmissions

on the same channel A necessary condition: two links incident on the same

node can not be activated simultaneously on the same channel

A sufficient condition: SNIR is above the desired threshold α

COROLLARY 1. G’

T in G(V, E) is feasible if every vertex of the corresponding

interference graph G’(V’, E’) satisfies:

A CBchannel 1 channel 1

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Example of corresponding

interference graph

0.2

0.4

0.3

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Fair scheduling algorithm

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Channel allocation algorithm

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Example of fair scheduling and channel allocation

gateway

a b

c d e

l

g

m

h

no

i

f

kj

p

channel 1

channel 2

channel 3

channel 4

1-hop level

capacity rank

1 2

2-hop level2

3 13

44

32

2

1

3 2

3

1

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Example of fair scheduling and channel allocation

gateway

a b

c d e

l

g

m

h

no

i

f

kj

p

1 2

23 1

3

44

32

2

1

3 2

3

1

queue length rank

e (n, o)

e (f, j)

e (b, e)

e (gw, a)

transform interference

e (n, o) = 0.3

e (f, j) = 0.2

e (b, e) = 0.4

e (gw, a) = 0.3

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Performance evaluation

Comparing with 802.11 CSMA/CA access scheme

Implemented in ns-2 Transmission range of each node is 150m Carrier sense range of 300m Simulations are in the 800x800m2 area which

50 nodes are placed randomly

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Throughput Improvement Evaluation

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Fairness Evaluation

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Conclusion

Proposed fair scheduling and channel allocation algorithms to solve the interference problem

Improved system throughput and guarantees the fairness for all nodes

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Thank you